Inspirations: Journey to the Centre of the TARDIS

Steven Moffat wanted the longest ever story title, and the story could be any old rubbish as it didn't really matter.

Alternatively... 

The interior of the TARDIS had hardly been touched since the series was revived apart from the odd bit of dialogue about swimming pools and wardrobes. The Christmas Invasion had shown the Tenth Doctor selecting his new outfit - but it was clearly recorded on the usual standing console room set.

Apart from bland corridors and a handful of rooms (Zero Room, Power Room, bedroom / sleeping areas, boot room...), the classic iteration of the series hadn't shown much either.

That was apart from The Invasion of Time - but that had proven to be a major disappointment.

Action in this 1978 story moved inside the ship for much of the final 40 minutes, and many of these scenes were scheduled for the studio. However, industrial action meant the loss of studio time and, to save the story from outright scrapping, they were shifted to location - external filming being unaffected by the strike action.

The location chosen was a decommissioned mental hospital in Surrey - so the TARDIS appears to have lots of corridors designed along the lines of the old Victorian institutions. We did actually get to see the swimming pool for a change - filmed at a business property in Hammersmith.

All that brickwork, and the all too obvious location filming, disappointed everyone who saw it.

This was one of the things Moffat wanted to redress when it came to the 50th Anniversary year, though he opted not to write the story himself. That dubious pleasure went to Stephen Thompson, who had previously written the underwhelming Curse of the Black Spot. (Quite how you can write a boring pirate story, no-one knows). Thompson was working with Moffat and Gatiss on Sherlock.

His own idea for a submission was actually a prequel to Robots of Death, delving into Taren Capel's childhood.

His first idea once he'd accepted Moffat's brief was that the TARDIS would collide and meld with another space / time machine - creating a set of weird, surreal interfaces. The pilot of the other vessel was actually wanting to steal the TARDIS. The second idea was a collision with a school trip in space, and the TARDIS would be overrun by teenagers - so this could have been an awful lot worse.

Luckily Moffat hated the idea.

The ship being captured by a salvage team who only could only see the value of its components was Thompson's third idea.

The story title obviously derives from Jules Verne's 1864 novel Journey to the Centre of the Earth, most memorably adapted for cinema in 1959 with James Mason and Pat Boone.

It was Moffat who suggested the image of the TARDIS engines exploding but frozen in mid-blast, after seeing Rebecca Horn's art installation "Concert for Anarchy" at the Tate. This involved an exploding piano.

Matt Smith suggested that the Doctor's bedroom be shown for the very first time, but this wasn't picked up.

References to old stories abound.

Components which the salvagers detect include dynomorphic generators (Time-Flight), a beam synthesiser (The Curse of Peladon) and a conceptual geometer (The Horns of Nimon).

The Doctor threatens to self-destruct the TARDIS, as he previously did in Attack of the Cybermen - though he claimed he'd made the self-destruct up in Victory of the Daleks.

Some more recent props such as the Doctor's cot and some model TARDISes made by Amelia Pond are seen as Clara wanders about the ship.

An astronomical observatory is seen, which has a telescope very similar to the one from Torchwood House (Tooth and Claw).

The Cloister Bell sounds (first heard in Logopolis). This story had also first mentioned the architectural configuration system. Once simply a function of the console, it's now a big tree-like thing.

We get to see the Eye of Harmony - initially something only to be found on Gallifrey (The Deadly Assassin) but then apparently a feature of all TARDISes (The Movie).

We hear snatches of speech in the library - some of Timothy Dalton's dialogue lifted from The End of Time Part 1.

As for the Series 7 story arcs, Clara sees a book entitled "The History of the Time War," which features the Doctor - presumably named. And the Doctor finally confronts her about her true nature.

Time gets reset, however, so both these things get forgotten.

Next time: The Flask of the Red Death...